How you prepare

Before you undergo external beam radiation therapy, your health care team guides you through a planning process to ensure that radiation reaches the precise spot in your body where it's needed. Planning typically includes:

Radiation simulation. During simulation, your radiation therapy team works with you to find a comfortable position for you during treatment.

It's imperative that you lie still during treatment, so finding a comfortable position is vital. To do this, you'll lie on the same type of table that's used during radiation therapy. Cushions and restraints are used to position you in the right way and to help you hold still.

Your radiation therapy team will mark the area of your body that will receive the radiation. Depending on your situation, you may receive temporary marking with a marker or you may receive small permanent tattoos.

Planning scans. Your radiation therapy team will have you undergo computerized tomography (CT) scans to determine the area of your body to be treated.

After the planning process, your radiation therapy team decides what type of radiation and what dose you'll receive based on your type and stage of cancer, your general health, and the goals for your treatment.

The precise dose and focus of radiation beams used in your treatment is carefully planned to maximize the radiation to your cancer cells and minimize the harm to surrounding healthy tissue.

Legal Conditions and Terms

Reprint Permissions

A single copy of these materials may be reprinted for noncommercial personal use only. "Mayo," "Mayo Clinic," "MayoClinic.org," "Mayo Clinic Healthy Living," and the triple-shield Mayo Clinic logo are trademarks of Mayo Foundation for Medical Education and Research.